Wheelchair lifts mounted on vehicles, such as buses, vans, motor homes and automobiles, provide wheelchair users access to the interior of the vehicles thereby increasing their mobility and enabling these people to become more self-reliant and independent. Wheelchair lifts have generally horizontal platforms which are used to support manual and motor driven wheelchairs along with persons located on the wheelchairs. Lift structures connected to the platforms operate to selectively raise and lower the platforms. When the platforms are in the lower or ground positions the wheelchairs are moved onto the platforms. The platforms are raised by the lift structures to a selected elevation, such as the floor of the vehicle, and then moved off the platform into the interior compartment of the vehicle. Actuators, such as electric motors, operating screws and hydraulic cylinders, are used to move the platforms to transport positions within the confines of the vehicle. The wheelchair is secured to the vehicle floor to prevent inadvertent movement of the wheelchair within the vehicle. In some vehicles, the wheelchair is moved to a vehicle operator position and anchored thereto to allow the wheelchair user to operate the vehicle. Examples of wheelchair lifts are disclosed in U.S. Pat. Nos. 4,096,955; 4,133,437; 4,664,584 and D440,728. The wheelchair lifts require modifications of the bodies of the vehicles and require considerable labor and installation costs.
Wheelchair lifts for motor vehicles do not utilize vehicle suspension devices for loading wheelchairs into the vehicle and unloading wheelchairs from the vehicle. Examples of vehicle body suspension systems are disclosed in the following U.S. patents. Keijzer et al in U.S. Pat. No. 4,067,558 discloses a motor vehicle wheel suspension strut for converting the conventional suspension unit to an air adjustable type suspension without discarding the original shock absorber and related components. This suspension strut does not allow the vehicle floor to be lowered when the vehicle is packed.
Danis in U.S. Pat. No. 6,098,995 discloses a motor vehicle suspension system for providing a kneeling function to a vehicle having a lowered floor for accommodating the loading and unloading of passengers. The suspension system includes a pair of springs and a pair of suspension members or shock absorbers operatively connected to the rear wheels of the vehicle for supporting the load on the vehicle. An air compressor supplies air to the shock absorbers. An exhaust valve associated with the air system allows air to exhaust from the shock absorbers whereby the vehicle floor moves down from above a normal height and allows all the air to exhaust from the shock absorbers whereby the vehicle floor moves down to the kneeling position above the support surfaces of the vehicle.
Air springs have been designed to fit directly into conventional rear coil spring mounts to support the rear portion of a motor vehicle, such as a truck, sport utility, wagon and motor homes. Conventional leaf springs have been replaced with parallel linkages and air springs to lower a vehicle's body to improve handling a load capacity. The air spring suspension systems maintain ground clearance and do not allow the vehicle's frame to be moved into engagement with the ground or vehicle support surface.